This invention relates to a method for producing a color filter and more particularly to a color filter suitable for use in a color liquid crystal display device or the like.
Methods for producing color filters generally used at present involve a dyeing method, a printing method, a pigment dispersion method, etc. wherein a transparent substrate is colored with a binder containing dyes pigments.
Since the dyeing method consists in selectively dying a thin film of a resin on a substrate with dyes, however, a resist printing process and a photolithographic process need to be performed each time the color is changed. Although resist printing is unnecessary with the above printing method, there is a limit to refinement of color patterns and, the larger is the number of colors, the precision of printing position becomes the worse. Although a fine color pattern is possibly obtainable with the pigment dispersion method, a high precision photolithographic process needs to be performed each time the color is changed, thus making the process extremely complicate.
For overcoming these deficiencies, there is proposed in Japanese Laid-open Patent Application No. Sho 59-114572 a method for producing a color filter by an electrodeposition coating method. With this method, a transparent electrode is prepared by patterning a transparent electrically conductive film deposited on the substrate, immersing the substrate in a colored electrodeposition bath, and applying electrical voltage only to a portion of the patterned transparent electrode to be dyed in the same color for forming a colored layer by electrodeposition. The substrate is then immersed in a different colored electrodeposition bath and electric voltage is then applied only to a portion of the substrate to be dyed in a different color for forming a different color layer by electrodeposition. In this method, however, it is necessary to first perform a high precision patterning of the transparent electrode, paying meticulous care to the patterned transparent electrode during the subsequent treatment. If part of the fine pattern should be broken, the subsequent coloring process is rendered difficult making production undesirable. Besides, the patterned transparent electrode needs to be electrically continuous, even in fine pattern sections, so that limitations are imposed on the degree of freedom of the pattern shape.